In Los Angeles – the city with the worst traffic – a 30-minute auto trip in traffic-free conditions becomes a 43-minute trip on Friday afternoons. That compares to 40.5 minutes on other weekday afternoons.

In comparison, the Friday congestion in many metro areas is relatively benign. In 43 of the 100 areas measured, less than two minutes were added to a 30-minute auto trip.

In fact, a quarter of commuters in the 10 metros with high Friday congestion opt out of traffic frustration by using transit, biking, or walking, or working at home.

Most of the top Friday congestion metros are very large, but not all. For example, Bridgeport, CT, ranks Number 5. In that case, long commuting distances are the cause, says David Schrank, an associate research scientist with the Texas Transportation Institute.

Friday afternoon tends to have the greatest congestion, Schrank said, because workers headed home are joined on the road by people leaving town. In addition, commuters tend to run more errands on the way home from work than during morning commutes.